Syntheses of model oligosaccharides of biological significance. XI. A short synthesis of fucosylated chitobiosides, also bound to asparagine in a synthon (as in N-linked glycoproteins)

1990 ◽  
Vol 68 (6) ◽  
pp. 953-957 ◽  
Author(s):  
Ho Huat Lee ◽  
Jose A. B. Baptista ◽  
Jiri J. Krepinsky
Keyword(s):  
Efficient Method ◽  
Biological Significance ◽  
Oligosaccharide Synthesis ◽  
Short Synthesis ◽  
Glycosylation Reaction

We describe a simple and efficient method for the preparation of the trisaccharide GlcNAc(β1-4)-[Fuc(α 1-6)-]GlcNAc(β 1-) (1) and of the protected form of GlcNAc(β 1-4)-[Fuc(α 1-6)-]GlcNAc(β1-Asn) (2). The key intermediate is benzyl 4,6-benzylidene chitobioside 5 giving the desired trisaccharide by insitu anomerization–glycosylation reaction with 2,3,4-tribenzylfucosyl bromide. The benzyl glycoside in the trisaccharide 6 has been replaced by acetate and then bromine; this glycosylating agent was used to prepare methyl and 8-methoxycarbonyloctyl glycosides as well as isothiocyanate 12, in a series of reactions. The latter compound gave, on reaction with 1-benzyl N-benzyloxycarbonyl-L-asparate, compound 13 (a protected derivative of 2), which should serve as a synthon for syntheses of glycopeptides. Keywords: glycopeptide, synthesis; oligosaccharide, synthesis; chitobiosides; fucosylated chitobiosides; N-linked oligosaccharides.

Facile Synthesis of Chalcone Glycosides Isolated from Aerial Parts of Brassica rapa l. ‘hidabeni'.

2018 ◽  
Vol 15 (3) ◽  
pp. 423-429
Author(s):  
Galal A. Elsayed ◽  
Ali Kh. Khalil
Keyword(s):  
Aldol Condensation ◽  
Biological Significance ◽  
Hydroxyl Groups ◽  
Synthetic Approach ◽  
One Pot ◽  
Aerial Parts ◽  
Synthetic Procedure ◽  
Glycosylation Reaction ◽  
Viable Method ◽  
Basophilic Leukemia

Background: The Cruciferous family of vegetables which includes Brassica Turnips showed antioxidant and hepatoprotective effects. The phytochemical investigations of the aerial parts of the traditional Japanese turnip vegetable (B. rapa L. 'hidabeni') revealed the presence of three chalcone glycosides, along with other glycoside components. As many natural products inhibited Ag-stimulated degranulation in cellular system, those chalcone glycosides have biological significance of suppressing antigen-stimulated degranulation in rat basophilic leukemia RBL-2H3 cells. Aim and Objective: Further investigation on the biological importance of those chalcone glycosides demands ample quantities of well-defined compounds. Therefore, we report herein a convenient and concise synthetic approach for the preparation of those chalcone glycosides. Materials and Methods: 4'-O-β-D-Glucopyransoyl-4-hydroxy-3'-methoxychalcone and 4'-O-(β-D-Glucopyransoyl)- 3',4-dimethoxychalcone were synthesized using a three-step strategy includes: i) O-glucosylation of 4-OH of 4'-hydroxy-3'-methoxy acetophenone (Acetovanillone); ii) introduction of the cinnamoyl residue by aldol condensation with p-benzyloxy benzaldehyde and p-methoxy benzaldehyde respectively; iii) full debenzylation of all the sugar hydroxyl groups. Meanwhile, 4,4'-Di-O-β-D-glucopyransoyl-3-methoxychalcone was synthesized by an alternative way where a double armed aglycon acceptor was utilized in a one pot double glycosylation reaction. Results: Constructing the target chalcone glycosides: 4'-O-β-D-Glucopyransoyl-4-hydroxy-3'-methoxychalcone, 4'-O-(β-D-Glucopyransoyl)-3',4-dimethoxychalcone and 4,4'-Di-O-β-D-glucopyransoyl-3-methoxychalcone were achieved in 13%, 14%, and 90% yields. Conclusion: A simple and practical synthetic procedure by which the target chalcone glycosides were synthesized could be a promising and viable method. Furthermore, this strategy could be utilized in the synthesis of various O-diglycosyl chalcones having more complicated structures.

Glycosylation by Alkyne Activation of the 2-O-Substituted Propargyl Group in a β-Phenylthioglucoside with a 5 S 1 Conformation

Synlett ◽  
2021 ◽  
Author(s):  
Kazutada Ikeuchi ◽  
Shintaro Matsumoto ◽  
Daiki Ikuta ◽  
Hidetoshi Yamada
Keyword(s):  
Hydroxy Group ◽  
Oligosaccharide Synthesis ◽  
Reaction Proceeds ◽  
Oxocarbenium Ion ◽  
Glycosyl Donor ◽  
Glycosylation Reaction

AbstractGenerally, glycosylation reactions activate an anomeric substituent in a glycosyl donor to generate an oxocarbenium ion intermediate. Here we report a novel glycosylation reaction triggered by the activation of a 2-O-substituted propargyl group in a 3,6-O-1,1′-[(ethane-1,2-diyl)bibenzene-2,2′-bis(methylene)]-β-thioglucoside. This reaction proceeds through a cationic Au(I)-mediated intramolecular migration of the anomeric substituent onto the alkyne moiety of the propargyl group, followed by α-attack by the hydroxy group in the glycosyl acceptor on the oxocarbenium ion. The migration of the anomeric group occurs selectively through a 6-exo-dig pathway. The 2-(phenylsulfanyl)prop-2-en-1-yl group produced during the glycosylation is removable under conditions similar to those used for removing an allyl group. This reaction will be developed for further applications in orthogonal oligosaccharide synthesis.

Syntheses of model oligosaccharides of biological significance. X.•Syntheses and NMR and mass spectral analysis of trideuteriomethyl di-3,6-O-(4-O-β-D-galactopyranosyl-2-acetamido-2-deoxy-β-D-glucopyranosyl)-β-D-galactopyranoside: the I antigen branchpoint penta- and tetrasaccharides and a related trisaccharide

1990 ◽  
Vol 68 (6) ◽  
pp. 942-952 ◽  
Author(s):  
Dennis M. Whitfield ◽  
Henrianna Pang ◽  
Jeremy P. Carver ◽  
Jiri J. Krepinsky
Keyword(s):  
Mass Spectra ◽  
Three Dimensional ◽  
Biological Significance ◽  
Dimensional Structure ◽  
Oligosaccharide Synthesis ◽  
Mass Spectral Analysis ◽  
Mass Spectral ◽  
Nmr Spectrometry ◽  
Synthetic Intermediates

As part of our studies of complex oligosaccharides, in particular their three-dimensional structure, we have synthesized the antigen I branchpoint penta- and tetrasaccharides. The unbranched trisaccharide 3D was also synthesized, and its derivative 3B served as the intermediate for the synthesis of higher oligosaccharides. NMR spectra of major intermediates as well as of the final oligosaccharides were completely assigned. Mass spectra of the synthetic intermediates and the final oligosaccharides were analyzed and compared with those of a similar group of oligosaccharides containing L-fucose, N-acetyl-D-glucosamine, and D-galactose. Certain observations were made that could be utilized in the interpretation of mass spectra for the structural determination of protected oligosaccharides during the synthesis. Keywords: oligosaccharide synthesis, I antigen, carbohydrate mass spectrometry, carbohydrate NMR spectrometry, Gal-GlcNAc oligomers.

Microstructural morphology of sphingolipid dispersions as investigated by freeze-fracture EM

1995 ◽  
Vol 53 ◽  
pp. 944-945
Author(s):  
Vitthal S. Kulkarni ◽  
Wayne H. Anderson ◽  
Rhoderick E. Brown
Keyword(s):  
Acyl Chain ◽  
Biological Significance ◽  
Freeze Fracture ◽  
Fatty Acyl ◽  
Fatty Acyl Moiety ◽  
Aqueous Dispersions ◽  
Head Groups ◽  
Lipid Species ◽  
Microstructural Morphology ◽  
Layer Chromatography

The biological significance of the sphingomyelins (SM) and monoglycosylated sphingolipids like galactosylceramides (GalCer) are well documented Our recent investigation showed tubular bilayers in the aqueous dispersions of N-nervonoyl GalCer [N-(24:lΔ15,cls) GalCer] (a major fatty acyl moiety of natural GalCer). To determine the influence of lipid head groups on the resulting mesophasic morphology, we investigated microstructural self-assemblies of N-nervonoyl-SM [N-(24:1 Δ15,cls) SM; the second most abundant sphingomyelin in mammalian cell membranes], 1- palmitoyl-2-nervonoyl phosphatidylcholine [PNPC] (the lipid species with the same acyl chain configuration as in N-(24: 1) GalCer) and also compared it with egg-SM by freeze-fracture EM.Procedures for synthesizing and purifying N-(24:1) GalCer, N-(24:1) SM, and PNPC have been reported . Egg-SM was purchased from Avanti Polar Lipids, Alabaster AL. All lipids were >99% pure as checked by thin layer chromatography. Lipid dispersions were prepared by hydrating dry lipid with phosphate buffer (pH 6.6) at 80-90°C (3-5 min), vigorously vortexing (1 min) and repeating this procedure for three times prior to three freeze-thaw cycles.

Ultrastructural Localization Study of Carcinoembryonic Antigen (CEA) in Gastric Cancer: Immunoelectron Microscopic Observation

1990 ◽  
Vol 48 (3) ◽  
pp. 252-253
Author(s):  
Dong Yuming ◽  
Yang Guanglin ◽  
Wu Jifeng ◽  
Chen Xiaolin
Keyword(s):  
Gastric Cancer ◽  
Intestinal Metaplasia ◽  
Cancer Cells ◽  
Microscopic Observation ◽  
Biological Significance ◽  
Ultrastructural Localization ◽  
Mucinous Carcinoma ◽  
Surface Glycoprotein ◽  
Tubular Adenocarcinoma ◽  
Pap Method

On the basis of light microscopic observation, the ultrastructural localization of CEA in gastric cancer was studied by immunoelectron microscopic technique. The distribution of CEA in gastric cancer and its biological significance and the mechanism of abnormal distribution of CEA were further discussed.Among 104 surgically resected specimens of gastric cancer with PAP method at light microscopic level, the incidence of CEA(+) was 85.58%. All of mucinous carcinoma exhibited CEA(+). In tubular adenocarcinoma the incidence of CEA(+) showed a tendency to rising with the increase of degree of differentiation. In normal epithelia and intestinal metaplasia CEA was faintly present and was found only in the luminal surface. The CEA staining patterns in cancer cells were of three types--- cytoplasmic, membranous and weak reactive type. The ultrastructural localization of CEA in 14 cases of gastric cancer was studied by immunoelectron microscopic technique.There was a little or no CEA in the microvilli of normal epithelia. In intestinal metaplasia CEA was found on the microvilli of absorptive cells and among the mucus particles of goblet cells. In gastric cancer CEA was also distributed on the lateral and basal surface or even over the entire surface of cancer cells and lost their polarity completely. Many studies had proved that the alterations in surface glycoprotein were characteristic changes of tumor cells. The antigenic determinant of CEA was glycoprotein, so the alterations of tumor-associated surface glycoprotein opened up a new way for the diagnosis of tumors.

RIBONUCLEOPROTEIN PARTICLES CONTAINING mRNA and pre-mRNA

1973 ◽  
Vol 74 (Suppl) ◽  
pp. S130-S167 ◽  
Author(s):  
O. P. Samarina ◽  
E. M. Lukanidin ◽  
G. P. Georgiev
Keyword(s):  
Structural Organization ◽  
General Scheme ◽  
Biological Significance ◽  
Mrna Transport ◽  
Ribonucleoprotein Particles ◽  
Mrna Precursor

ABSTRACT This paper is a review of the data concerning the nature, structural organization, properties and biological significance of the particles, containing mRNA and pre-mRNA (precursor of mRNA), i. e., (1) nuclear pre-mRNA-containing particles (2) free cytoplasmic mRNP (ribonucleoproteins), or informosomes (3) polysome-bound mRNP. Some new data on the comparison of nuclear and cytoplasmic particles, the nature of poly A-containing structures, involvement of informofers in Adenovirusspecific RNA transfer are presented. The general scheme of mRNA transport from nucleus to cytoplasm is discussed.

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